The present invention relates to circuits for shifting the phase of an applied input signal a predetermined number of degrees and, more particularly, to an integrated ninety degree electronic phase shift circuit.
There are many applications for phase shift circuits of the above referred type. For instance, phase shift circuits are routinely used in phase locked loops (PLL) to maintain a quadrature relationship between the voltage controlled oscillator of the PLL and the input signal applied thereto. An additional use for a phase shift circuit is in the video detector portion of a high performance color television wherein the video signal is recreated. In this latter application it may be necessary to shift the phase of the intermediate frequency video carrier signal by ninety degrees with respect to an oscillator signal to maintain an in-phase relationship therebetween in order to detect the video information.
In order to obtain a high performance phase shift circuit it is important that it be wide band while eliminating small phase errors associated with transistor small signal emitter resistances or at least have adjustable circuitry for compensating for these resistances.
Hence, a need exists for a high performance circuit of the type described above which can be adjusted for eliminating transistor small signal resistance affects which otherwise create undesirable phase errors.